1. Field of the Invention
This invention relates to the processing of a non-petroleum organic liquid such as fats, animal and vegetable oils; and more particularly to the improvement in color of such an organic liquid by a multistep treating process.
2. Description of the Prior Art
Many non-petroleum organic liquids (e.g., fats, vegetable and animal oils) are used for human consumption and other utilizations. The organic liquid can be purified chemically and mechanically to remove solids and to improve chemical properties, color, odor and enhance storage stability, to make it more suitable for ultimate utilization. Present day treatment of crude fat, animal and vegetable oils, as organic liquids, consist generally of the steps of refining, bleaching, and deodorization. The term "refining" refers to any purification treatment designed to remove undesired materials such as free fatty acids, phosophatides, or mucilaginous material, or other gross impurities in the organic liquid. The term "bleaching" is reserved for treatment designed solely to reduce the color of organic liquid. The term "deodorizing" is used for the treatment which has as its primary object to remove the traces of constituents which give rise to flavors and odors from the organic liquid.
The refining of an organic liquid usually employs aqueous reagents in the nature of alkali or acid to remove certain impurities, such as free fatty acids and certain color bodies. Also, the refining treatment can improve the color and odor characteristics of the organic liquid. For example, vegetable oils, especially those subjected to oxidization, suffer from increased red and yellow color components; however, the green color from chlorophyll is not affected. In the hydrogenation of the refined organic liquid, the organic liquid is admixed with a small amount of a hydrogenation catalyst in a finely dispersed state. For example, an amount of metal hydrogenation catalyst less than about 0.05% by weight is introduced into the organic liquid. Then, this mixture is subjected to superatmospheric hydrogen at elevated temperatures for a selected period of time until the desired reaction of the unsaturated and hydrogen reducible materials is reached in the organic liquid. After hydrogenation is completed, the organic liquid carrying the dispersed hydrogenation catalyst is passed through precoated leaf filters for the removal of the metal hydrogenation catalyst. AS is apparent, the nature of filtration will result in a small amount of the metal hydrogenation catalyst being carried with the filtered organic liquid. In many instances, the residual amounts of metal hydrogenation catalysts must be removed by subsequent steps, whic are usually termed "post bleaching", which the residual taces of the metal hydrogenation catalyst are removed through the use of metal scavengers or compounds capable of forming inactive complexes with the metal component. These materials include certain acids such as phosphoric acid and organic acids such as citric and tartaric acids. Naturally, the post bleaching treatment of the hydrogenated organic liquid requires additional filtration with the selected addition of materials such as Filteraid to promote the substantial complete removal of the residual amounts of metal hydrogenation catalyst.
Although hydrogenation of organic liquid improves color relating to yellow and red components, it unfortunately does not remove the pronounced green color from vegetable oil, especially soybean oil. This green color in hydrogenated vegetable oil is most unacceptable in products to be used for human consumption, i.e., edible oils. At the present time, color improvement in an organic liquid is obtained by the use of selected additions of very finely dispersed solid adsorbent into a filtered hydrogenated organic liquid under conditions whereby the color bodies are adsorbed by the solid adsorbent. The organic liquid containing the solid adsobent must again be filtered after the addition of Filteraid material, so that the solid adsorbent is removed. Naturally, each filtering step involves the loss of product even with careful operation under the state of present day mechanical filtration technology.
Color improvement in organic liquid comes within the definition of bleaching treatment. Many types of materials are employed for this purpose. For example, bleaching earth, activated carbon, acid-activated earth and spent hydrogenation catalyst can be employed. However, the problem in conducting the bleaching treatment, as in refining, also involves mechanical filtration procedures to remove the dispersed solids from the purified organic liquid. The same filtration problems additionally exist in the deodorization treatment where a solid dispersed material is employed. Any introduction into the organic liquid of a solid material in a finely dispersed state requires presently a subsequent mechanical filtration step which must be conducted very carefully so that the ultimate degree of removal is obtained without unduly high product losses.
The present invention is a process which employs a combination of steps familiar in everyday practices in the refining and decoloring of organic liquids. However, there are added certain novel steps whereby the resultant combination of steps produces the desired refining and decoloring and/or deodorizing treatments without mechanical filtration of the organic liquid. Furthermore, substantially complete removal of even small amounts of finely divided solid mateials is obtained by uncomplicated procedures and equipment. In addition, the problems involved with oxidization of the organic liquid during mechanical filtration are avoided to insure optimum color and odor characteristics in the organic liquid.